1. Field of the Invention
The present invention relates to a method of forming an insulating film in a semiconductor device and, more specifically, to a method of forming an insulating film in a semiconductor device by which an insulating film is made to be a porous low dielectric constant insulating film.
2. Discussion of Related Art
An insulating film is formed between metal wirings to electrically isolate neighboring metal wirings. In this case, the structure of the metal wiring/the insulating film/the metal wiring is similar to the structure of the top electrode/the dielectric film/the bottom electrode of the capacitor, a parasitic capacitor is formed. For this reason, there is a problem that the operating speed of the device is lowered due to RC delay generated by resistive components and parasitic capacitance of the metal wiring. In addition, as an electrical signal transferred through the metal wiring is affected, reliability of the device is lowered.
For this reason, in order to overcome the above problems, the insulating film formed between the metal wirings is made to be a low dielectric constant insulating film having a low dielectric constant. In this case, however, the distance between the wirings becomes narrow due to an increased level of integration. Therefore, there are limitations to preventing the parasitic capacitor for being formed by means of a method of lowering a total dielectric constant by forming an insulating film using a material of a low dielectric constant.
In recent years, in order to overcome this problem, a porous low dielectric constant insulating film in which air having the lowest dielectric constant is contained is formed. In the course of forming a contact hole (or a via hole) or a trench in the porous low dielectric constant insulating film through a dual damascene process, chemicals used to etch the insulating film are introduced into pores of the porous low dielectric constant insulating film and remain therein.
As such, if the chemicals remain in the pores, metal wirings formed in a subsequent process are eroded by the chemicals. This may cause fail of the device, etc. Accordingly, it is required to form a dense film on the surface of the porous low dielectric constant insulating film. For this reason, the process steps become complicated and the process time is lengthened.